Joe Biden says it is "clear" he is on track to win the US presidency, as he clinched a second state from the Republicans.
At a speech in Delaware, the Democrat presidential candidate insisted "I'm not here to declare that we've won" but pointed out he is on course to take key battlegrounds by bigger margins than Donald Trump did in 2016.
In Wisconsin, the first state he looks set to flip from red to blue, Mr Biden said he had won by 20,000 votes - "virtually the same margin that President Trump won that state [by] four years ago".
And in Michigan, another razor-tight race he is projected to win, he claimed to be leading by 35,000 votes - a "substantially bigger margin" than Mr Trump won it by last time.
"It is clear we are winning enough states to reach 270 electoral votes", Mr Biden said - referring to the crucial number both candidates are chasing to guarantee them a win.
"We the people will not be silenced; we the people will not be bullied; we the people will not surrender."
But Mr Trump's campaign manager has vowed to "immediately" request a recount in Wisconsin due to "reports of irregularities" in some counties.
Counting continues across several other swing states - with the race to the White House still too close to call.
Mr Biden is also ahead in Arizona (11 electoral votes) and has already won 69.8 million votes nationwide - a new record for any presidential candidate.
Mr Trump is leading in Georgia (16), North Carolina (15) and Nevada (6), and has had 66.8 million votes across the country - more than three million more than he achieved last time.
In a bid to derail two potential losses, the Trump campaign has filed lawsuits to try and halt counting in Michigan and Pennsylvania.
They claim their election observers have "not been provided with meaningful access... to observe the opening of ballots" and that there has not been enough "meaningful transparency".
Mr Biden failed to make the early breakthroughs he was hoping would hand him a decisive lead on election night.
States like Ohio, Florida, Iowa and Texas remained red, significant tightening the Democrat challenger's options for reaching the prized 270 electoral college votes.
That led to Mr Trump claiming victory and accusing his political opponents of a "fraud on the American public", without evidence.
He used an address to the nation to declare he is taking his fight to the Supreme Court, then fired off a flurry of tweets about the slowly-progressing results in the remaining undeclared states.
"How come every time they count Mail-In ballot dumps they are so devastating in their percentage and power of destruction?" he asked.
In another post, he wrote: "Last night I was leading, often solidly, in many key states, in almost all instances Democrat run and controlled.
"Then, one by one, they started to magically disappear as surprise ballot dumps were counted."
Vote totals are being updated as more votes are counted and there has been no evidence of ballot dumping.
Twitter has had to step in to censor several of Mr Trump's messages, warning readers: "Some or all of the content shared in this Tweet is disputed and might be misleading about an election or other civic process."
